<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        * {
            padding: 0;
            margin: 0;
        }
        .search {
            position: relative;
            width: 178px;
            margin: 100px;
        }
        .con {
            position: absolute;
            display: none;
            top: -40px;
            width: 171px;
            border: 1px solid rgba(0,0,0,.2);
            box-shadow: 0 2px 4px rgba(0,0,0,.2);
            padding: 5px 0;
            font-size: 18px;
            line-height: 20px;
            color: #333;
        }
        .con::before {
            content: '';
            width: 0;
            height: 0;
            position: absolute;
            top: 28px;
            left: 2px;
            border: 8px solid;
            border-color: #fff transparent transparent;
        }
    </style>
</head>
<body>
    <div class="search">
        <div class="con"></div>
        <input type="text" placeholder="请输入您的快递号" class="jd">
    </div>
    <script>
        let con = document.querySelector('.con');
        let jd = document.querySelector('.jd');

        jd.addEventListener('keyup',function () {
            if (this.value) {
                con.style.display = 'block';
                con.innerHTML = this.value;
            } else {
                con.style.display = 'none';
            }
        });

        jd.addEventListener('focus',function () {
            if (this.value) {
                con.style.display = 'block';
            } else {
                con.style.display = 'none';
            }
        });
        jd.addEventListener('blur',function () {
            con.style.display = 'none';
        });
     </script>
</body>


